1. Field of the Invention
The present invention relates to an electric wire for an automobile, particularly relates to an electric wire for an automobile constituted by slender wire formation and light-weighted formation and promoting reliability of connection.
2. Description of the Related Art
In an automobile, there is used a wire harness which bundles a number of electric wires for electrically connecting to an electric equipment or the like. An electric wire conductor in the wire harness requires its tensile strength to be equal to or larger than about 60 N/mm2 in view of workability. A sectional area (hereinafter, also referred to as “conductor size”) equal to or larger than 0.35 mm2 is required in case of a single electric wire.
There is the electric wire for a wire harness having a conductor in a twisted wire structure constituted by twisting together a plurality of wires. FIG. 1 shows an example of the conductor. In FIG. 1, numeral 1 designates the conductor which is constituted a twisted wire structure arranging 6 surrounding wires 3 to surround a central wire 2 to twist together. In a related art, it is known to use copper or a copper alloy for both of the central wire 2 and the surrounding wire 3 constituting the conductor with the twisted wire structure.
In an automobile in recent years, slender wire formation (for example, the conductor size equal to or smaller than 0.22 mm2) and light-weighted formation of an electric wire used have been requested. However, when a conductor (central wire, surrounding wire) uses copper or a copper alloy, a required tensile strength cannot be achieved by the slender wire formation and light-weighed formation.
Hence, JP-UM-A-6-13014 discloses that the conductor uses a composition of both copper or a copper alloy and stainless steel for wires in order to achieve the slender wire formation and light-weighed formation. The composition has stainless steel as a central wire and a plurality of surrounding wires made of soft copper are arranged to surround the central wire so that twisted wire structure of the composition is formed. Since stainless steel is provided with a small specific weight in comparison with that of copper or a copper alloy and stainless steel is provided with a tensile strength, slender wire formation and light-weighted formation are achieved.
However, in the case of the electric wire having the conductor as described in the publication, when the electric wire is pressed at a connecting portion, stainless steel constituting the central wire in a conductor barrel of a connecting terminal may not be crushed but shifted from a central position. A reliability of connection is insufficient. In this way, there is desired to realize a technology achieving a required tensile strength, achieving slender wire formation and light-weighted formation and ensuring reliability of connection.